KIN 100 1st Edition Lecture 3 Muscle● Different subdisciplines study different aspects of a topic○ exercise physiology-metabolism○ biomechanics- morphology○ motor control- activation● Muscle anatomy○ ○ Motor Unit- a motor neuron and all of the muscle fibers it innervates■ each muscle fiber responds to only one motor neuron○ Neuromuscular junction (NMJ)- connection between the neuron and the muscle● Types of muscle fibers○ fast-twitch- high force; short period of time- easily fatigable■ type 2■ anaerobic metabolism■ few capillaries- appears white- “white muscle”○ slow-twitch- low force; long time- fatigue resistant■ type 1■ aerobic metabolism■ many capillaries- appears red- “red muscle”● Motor Unit MorphologyMuscle #motor units Innervation ratioeye muscles (6) 3000 10gastrocnemius 600 2000(calf muscle)● Innervation ratio- number of muscle fibers per motor neuron○ eye muscles have much more fine control- many motor units, each unit controls few muscle fibers● Muscle biopsy-small piece of muscle removed and stained for study○ studied for different reasons● Physiology of muscles■ contraction time● shorter in fast-twitch● longer in slow-twitch● Muscle contraction■ Myosin and Actin- proteins in muscle fibers■ Acetylcholine- neurotransmitter● released from vesicles in motor neuron and actives the muscle fiber by hitting the receptors1. Nerve action potential(AP)2. Acetylcholine(ach) released from vesicles3. Ach binds to muscle receptor sites4. Muscle fiber AP generation5. AP travels along muscle fibers6. Ca+ released in muscle fibers7. Ca+ causes actin-proteins8. Muscle contraction- shortening of muscle fibers■ Action potential- electronic signal sent through cells○ myosin crossbridges- pull actin filaments alongMuscle Contraction Pathology■ Myasthenia gravis- receptor sites are not fully developed● harder to receive messages/ signals■ ALS (Lou Gehrigs Disease)- number of motor neurons decrease● impaired muscle contractionTypes of Muscle Contraction○ Isometric (static) contraction- no movement/change in joint angle○ Isotonic (dynamic)- muscles move■ Concentric- muscle shortening■ Eccentric- muscle lengtheningMeasuring Muscle Strength○ Isometric- maximal force (pushing against a wall)○ Isotonic- repetition maximum (RM)- max weight you can lift a set number of
View Full Document
Unlocking...